Modes of axial collapse of unconstrained capped frusta

Efforts are made to classify the modes of deformation of unconstrained capped end frusta when crushed axially between two parallel plates. Tens of aluminum spun capped end frusta of different semi-apex angles (15–60°) and thicknesses (1–3 mm) are crushed at quasi-static loading conditions using a universal instron machine. The resulting modes of deformation can be classified into: (1) outward inversion, (2) limited inward inversion followed by outward inversion, (3) full inward inversion followed by outward inversion, (4) limited extensible crumpling followed by outward inversion, and (5) full extensible crumpling. Samples of frusta made of low carbon steel sheets and nylon plastic were tested statically and gave similar results. An explicit version of ABAQUS 5.8 finite element (FE) program is used to model the crushing modes. Good agreement is obtained between the FE predictions and the experimental work.